Communication devices, particularly portable communication devices such as handheld two-way radios, are typically powered by rechargeable battery packs containing a plurality of battery cells. These battery packs or cells may be coupled internally or externally to the portable product which operates as a host device. With the advances in technology, usable cell voltage ranges are extending beyond the operational input voltage ranges of communication products. Factors such as cell size, weight, battery capacity, voltage range, battery cut-off voltage, and battery load current are all important considerations in the design and development of portable products as well as in the design of charger devices needed to support the charging of the batteries.
As newer cell technologies become available, it is desirable to incorporate new battery cells into future and existing (legacy) product lines. However, legacy host devices operating on a limited voltage range, for example, at a voltage range between 5.6-8.4V, are unable to fully utilize the capacity provided by newer rechargeable battery cells, such as lithium-ion cells for which the useful voltage can be extended as high as 4.5V or as low as 2.0V per cell. This is due to the fact that most host devices will perform a low-voltage shutdown at a particular threshold voltage (for example, at a voltage less than 5.7V) prior to fully discharging the newer technology battery cells. Also, the host devices are designed for a particular maximum input voltage (e.g., 8.4 V) and may not efficiently utilize higher voltages afforded by newer-technology cells (e.g., 9.0 V when two 4.5V cells are used in series). Another problem with the use of newer cells is the need to reduce battery load current when the battery is at a low state of charge thereby minimizing voltage losses due to series resistance in the battery or host device.
Accordingly, there is a need for a means to adapt the newer battery cells/packs for host device and charger operation over narrower low voltage ranges.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.